Clamping device or chuck

ABSTRACT

A clamping device for easily and quickly releasing or firmly securing a rotary cutting or grinding tool such as a burr, bit, or the like to a rotatable drive shaft having a longitudinallyextending, tool-shaft-receiving bore at its outer free end for reception of the shaft of rotary cutting tools such as burrs, bits, and the like. A cylindrically-shaped insert of resilient material (e.g. rubber) is disposed axially relative to the drive shaft and in a counter-bore at the free end of said drive shaft, said insert having an axial bore therethrough of approximately the same diameter as the outside diameter of the shaft of the cutting tool, so that the cutting tool shaft can be slipped into and out of the insert bore and the bore of the drive shaft. A plurality of steel balls are disposed in radial bores in the wall of the counter bore of the drive shaft, and there is cam means slideable on the drive shaft for forcing the balls into the insert to thereby compress parts of the insert onto the shaft of the cutting tool and to thereby effect operable clamping of the cutting tool shaft in the clamping device. Sliding the cam means in one direction effects clamping of the cutting or grinding tool shaft in the device, and sliding such cam means in the opposite direction effects release of said cutting or grinding tool shaft so that said cutting tool may be readily removed from the clamp device. As used herein, the term rotary cutting tool or tools includes various cutting tools such as, for example, bits, burrs, rotary grinding tools and the like.

United States Patent 1 Speed 1 Oct. 2, 1973 l l CLAMPING DEVICE OR CHUCK[75] Inventor: Russell H. Speed, Reno, Nev.

[73] Assignee: Standard Pneumatic Motor Company, Reno, Nev.

[22] Filed: Feb. 25, 1972 [21] Appl. No.: 229,524

Primary ExaminerGil Weidenfeld Alt0rney-J. Carroll Baisch [57] ABSTRACTA clamping device for easily and quickly releasing or firmly securing arotary cutting or grinding tool such as a burr, bit, or the like to arotatable drive shaft having a longitudinally-extending,tool-shaft-receiving bore at its outer free end for reception of theshaft of rotary cutting tools such as burrs, bits, and the like, Acylindrically-shaped insert of resilient material (eg rubber) isdisposed axially relative to the drive shaft and in a counter-bore atthe free end of said drive shaft, said insert having an axial boretherethrough of approximately the same diameter as the outside diameterof the shaft of the cutting tool, so that the cutting tool shaft can heslipped into and out of the insert bore and the bore of the drive shaft.

A plurality of steel balls are disposed in radial bores in the wall ofthe counter bore of the drive shaft, and there is cam means slideable onthe drive shaft for forcing the balls into the insert to therebycompress parts of the insert onto the shaft of the cutting tool and tothereby effect operable clamping of the cutting tool shaft in theclamping device. Sliding the cam means in ,one direction effectsclamping of the cuttingv or grinding tool shaft in the device, andsliding such cam means in the opposite direction effects release of saidcutting or grinding tool shaft so that said cutting tool may be readilyremoved from the clamp device.

As used herein, the term rotary cutting tool or tools includes variouscutting tools such as, for example, bits, burrs, rotary grinding toolsand the like.

12 Claims, 4 Drawing Figures CLAMPING DEVICE OR CHUCK BACKGROUND OF THEINVENTION 1. Field of the Invention This invention relates generally toclamping devices and relates more particularly to a device for clampingrotatable cutting tools and the like to rotary drive shafts.

2. Description of the Prior Art There are various types of clampingdevices such as chucks having metal jaws and some having metal ballsadapted to be forced against the metal shafts of cutting devices.However, in all of these devices, as far as I am aware, the jaws orballs have metal-against-metal contact and require very closetolerances, or require notches in the cutting tools shaft or specialconfigurations other than a plain round shaft.

SUMMARY OF THE INVENTION The present invention comprises a clampingdevice for clamping the plain, round shafts of rotary cutting tools andthe like to rotary drive shafts adapted to be operably connected to asource of power. The drive shaft has a longitudinallyextending bore atits outer end for reception of the shaft of the cutting tool. There is aresilient insert disposed axially relative to the drive shaft in anaxial counter-bore at the free end of the drive shaft, the insert havingan axial bore or passage therethrough of approximately the same diameteras the outside diameter of the shaft of the cutting tool, so that thecutting tool shaft can be slipped easily and quickly into and out of theinsert bore and the bore of the drive shaft when the clamping device isin the release position.

There are a plurality of radial bores in the wall of the counter-bore ofthe drive shaft, and there is cam means slideable on the drive shaft forforcing the balls into the insert to thereby compress portions of sameonto the shaft of the cutting tool and effect operable clamping of thecutting tool shaft in the clamping device and, hence, to the driveshaft. Sliding the cam means in one direction effects clamping of thecutting tool or grinding tool shaft in the deviceand sliding such cammeans in the opposite direction effects release of the cutting orgrinding tool shaft.

There is a threaded-nut arrangement engageable in the end of therotatable driving shaft which may be adjusted so as to control thelength of the counter-bore in which the resilient insert rests. Thisadjustable feature serves a dual purpose: (1) It enables compensationfor tolerance variation on thelength of the insert, and (2) it permitsthe counterbored chambers volume to be set precisely so as to accuratelycontrol the space into which the resilient insert may expand in an axialdirection under compression.

This second feature is extremely important because, if the'cavitycontaining the insert is too long, the resilient material will bepermitted to expand too far in the axial direction and, consequently,fail to place sufficient force on the cuttingtool's shaft or shank whenthe sliding collar is moved to the secured position.

If, on the other hand, too little axial expansion is permitted, movementof the sliding collar to the engaged or secured position is renderedimpossible, due to the resistance encountered when the insert hasreached its limit of compressability.

The nut has an axial bore therethrough of approximately the samediameter as the diameter of the bore in the drive shaft for operativereception of the shaft of the cutting tool to be secured to the driveshaft. When the cutting tool shaft is disposed in the bores of the nut,insert and drive shaft, the cutting tool shaft is held in axialalignment in the bore of the nut and the bore in the drive shaft.Pressure on the cutting tool shaft through the insert by the ball orballs will notcause any misalignment of the cutting tool shaft orwobbling of the cutting tool shaft.

OBJECTS AND ADVANTAGES OF THE INVENTION It is an object of the presentinvention to provide a clamping device for cutting tools such as bits,burrs and the like wherein the shafts of such cutting tools may beeasily insertedinto and removed from the clamping de vice.

Another object of the invention is to provide a clamping device of thischaracter wherein little or no pressure on the cutting device is neededto insert it into or remove it from the clamping device.

Still another object of the invention is to provide a device of thischaracter wherein torque or twisting movement of the cutting tool in theclamping device is practically impossible when the clamping device isengaged.

A further object of the invention is to provide a device of thischaracter whereby clamping may be quickly and easily effected andwhereby quick and easy release may also be effected.

A still further object of the invention is to provide a resilient insertwhereby the effective clamping parts are not metal to metal.

Another object of the invention is to provide a device of this characterwherein the resilient insert is easily removable for replacement.

Still another object of the invention is to provide a device of thischaracter having means to adjust or vary the volume of the chambercontaining the insert for the purpose of compensating for lengthtolerance of the insert as well as providing a means of varying the gripforce applied to the insertable cutting tool.

A further object of the invention is to provide a device of thischaracter that does not require very close tolerances. I

V A still further object of 'the invention is to provide a device ofthis character that is relatively inexpensive to manufacture.

Another object of the invention is to provide a device of this characterthat has a variety of uses such as for deburring tools, dental tools,tools for hobby use and the like.

The characteristics and advantages of the invention are furthersufficiently referred to in connection with the following detaileddescription of theaccompanyind drawings and represent certainembodiments. After considering these examples, a skilled person willunderstand that many variations may be made without departing from theprinciples disclosed and I contemplate the employment of any structures,arrangements or modes of operation that are properly within the scope ofthe appended claims.

BRIEF DESCRIPTION OF THE DRAWING Referring to the drawing, which is forillustrative purposes only:

FIG. 1 is a longitudinal section through a clamping device embodying thepresent invention, the clamping device being shown in the releaseposition;

FIG. 2 is a sectional view taken on line 22 of FIG.

FIG. 3 is a longitudinal section through the clamping device showing theshaft of a cutting tool disposed therein and with the device in theclamping position; and

FIG. 4 is a view similar to FIG, 3 showing an alternative arrangement.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring more particularly tothe drawing, there is shown an end portion of a tool embodying thepresent invention. The tool shown is merely for illustrative purposes,and could be of any size, shape or configuration. A rotatable shaftextending from the front of any tool could be modified to incorporatethe principles herewith disclosed.

A shaft extends outwardly beyond the forward face of the tool 10. Ashaft part 11 has an axial rotatable tool shaft bore 12 therein which isenlarged at 13 and comprises an insert housing bore and is furtherenlarged at 14, the enlarged part 14 being an internal thread relief.From the thread relief 14 to the shaft 11 forward termination, the shaft11 is internally threaded 15. The tool shaft bore 12 is sufficientlydeep in shaft 11 to accept the longest cutting tool shank contemplatedfor usage in the tool. The external configuration of the portion ofshaft 11 which lies within the tool 10 is optional, requiring only thatthe smallest outside diameter in the area of the tool shaft bore 12 beof sufficient size to permit a reasonable wall thickness around too]shaft bore 12.

Within the enlarged part 13 of the shaft part 1] is a resilient insert16 of any suitable material. It has been found that very satisfactoryresults are obtained by having the insert of rubber and the rubber maybe 70 shore, although it is not limited thereto. The insert has an axialbore 17 therethrough of substantially the same diameter as the bore 12in the shaft part 11.

A retainer nut 18 has an externally-threaded part 19 screwed into theenlarged, internally-threaded part of the shaft 1]. Nut 18 has anenlarged head 20 of any suitable shape. However, some portion of thishead must protrude radially outwardly a distance sufficient to limit theforward travel of the collar 26. The inner end of the nut 18 has aninward extension 21 that has a diameter slightly smaller than thediameter of the enlarged bore 13 of the shaft, so that said extension 21may enter into the bore 13. Normally, the free end of the extension 21is just at the entrance of the bore 13 and it may be said that said freeend of the part 21 is flush with the entrance of bore 13. With thisarrangement, the insert is properly and securely positioned and retainedin the bore 13 and, if it is desired to reduce the axial length of thebore 13 of the shaft, the nut may be screwed further into the end of theshaft 11 with the extension 21 effecting the reduction of the axiallength of bore 13. When the insert is compressed by moving the collar 26to its forward position shown in FIG. 3, its

inner end is forced into the space 22 which flairs outwardly from thetool shaft bore 12 of the shaft to the insert bore 13 thereof. The nuthas a bore 23' extending longitudinally therethrough of the samediameter as the bore 17 of the insert, when the latter is not undercompression, and the diameter of the bore 12 of the shaft.

Shaft 11 has a plurality of radial bores 24 intermediate the ends of theinsert bore 13 and connected therewith at their inner ends. .In theradial bores 24 are steel balls 25. The diameter of each of the radialbores 24 is slightly greater than the diameter of the balls, and thediameter of said balls is greater than the thickness of the wall of theshaft defining the insert bore 13 so that, normally, the balls extendoutwardly of the shaft portion defining the insert bore 13.

On the shaft 11 there is a collar, indicated generally at 26, of lesslength than the distance from the forward face of tool 10 to the nuthead 20, said collar being slideable on the shaft 11. The outer end ofthe collar has a bore 27 of sufficient diameter to receive the balls 25,and at the inner end of said bore 27 there is an annular cam 28 whichmay be termed the collar cam. Cam 28 tapers inwardly and when the collar26 is moved from its inner release position, shown in FIG. 1, to itslocking position, shown in FIG. 3, the collar cam 28 engages the balls25 and forces them inwardly in their radial bores 24, so that said ballscompress those parts of the insert 16 with which they come intoengagement. When the collar is moved to its outer locking position, asshown in FIG. 3, the inner end portion 29 of the collar holds the balls25 in the locking position. Movement of the collar to its inner positionwill allow the balls to be forced outwardly by the resilience of theinsert to the release position shown in FIG. 1.

In FIG. 3, there is shown the shaft or stem 30 of the cutting tooldisposed in the bores 23, 17 and 12. The collar 26 is shown in thelocking position with the balls 25 at the inner position and compressingthe insert on the shaft 30. It will be noted that the inner end of theinsert is forced at least part way into the space 22 when compressed.

Any suitable number of balls may be used, there being 3 shown in thearrangement of FIGS. 1, 2 and 3. The device will work with but a singleball or with two balls, although it is preferred that at least threeballs be used.

In the embodiment of FIG. 4, the parts that are the same as in thearrangement shown in FIGS. 1, 2 and 3 will have the same referencenumerals. The difference between the embodiment of FIG. 4 and theembodiment of FIGS. 1, 2 and 3 is in the collar which is indicatedgenerally at 26-A in FIG. 4. This collar 26-A has an annular collar cam,indicated at 28-A, which is reversely inclined relative to the collar26. The collar 26-A is slideable on the outer end portion of the shaft11 and includes the part 29-A corresponding to the part 29 of the collarshown in FIGS. 1, 2 and 3.

With this arrangement, the clamp is in the release position when thecollar is at its outer limit of movement, and in the clamping positionwhen said collar is at its inner limit of movement. However, thisarrangement has the addition of a suitable means, indicated at 31, tolimit the collars inner movement so as to prevent the rear face of thecollar from contacting the forward face of the tool 10. FIG. 4 showsthis collar stop device 31 as a separate ring pressed onto the outsidediameter of shaft 11, though it could be an integral part of the shaftitself. A further possibility may be to use a snap ring to limit therearward travel of the collar.

In FIG. 4, it is to be noted that there are four balls used and, ofcourse, even more may be provided.

In FIG. 1, the forward face of the tool limits inward movement of thecollar. In FIG. 4, the collar stop part 31 accomplishes this task. Thehead 60 of the nut limits outward movement of said collar.

With the arrangement shown in FIGS. 1, 2 and 3, the three balls exertgreat forces at three pressure points on the burr shaft portion directlybeneath the balls when the collar 26 is in the locking position, therebyfirmly clamping the cutting burr or the like to the drive shaftassembly. When the collar is moved to the release position, theresilience of the rubber insert pushes the metal balls outwardly so thatthey follow the incline of the collar cam to the outer position shown inFIGS. 1, 2 and 3, thereby releasing the pressure on the cutter shaft sothat the cutter may be easily removed by pulling out the shaft. Theshaft may, of course, be easily and quickly inserted into the boresprovided therefor, and said shaft then easily and quickly is clamped inoperative position. With the four-ball arrangement of FIG. 4, there arefour pressure points for clampingly securing the cutting tool shaft tothe drive shaft. With either arrangement or I with arrangements having adifferent number of balls, torque or twisting movement of the cuttershaft 30 is practically impossible when the clamp is in the clampingposition.

The insert is very simple and can be easily removed and easily replaced.

The invention and its attendant advantages will be understood from theforegoing description and it will be apparent that various changes maybe made in the form, construction and arrangement of the parts of theinvention without departing from the spirit or scope thereof orsacrificing its material advantages, the arrangement hereinbeforedescribed being merely by way of example, and I do not wish to berestricted to the specific form shown or uses mentioned except asdefined in the accompanying claims.

I claim:

1. A clamping device for operably holding rotatable tools, comprising:

a drive shaft adapted to have one end connected to a source of power andhaving its other end free, said drive shaft having a free end portionwith a tool shaft bore extending axially from its free end for operablereception of the shaft of a rotatable tool, said bore having an enlargedinsert housing bore adjacent the free end of said drive shaft, therebeing at least one radial bore extending from the surface of the shaftinto the enlarged insert housing bore;

a resilient cylindrical insert in said insert housing bore, said inserthaving an axial bore therethrough of substantially the same diameter asthe tool shaft bore and axially aligned therewith;

means for retaining said insert in said insert housing bore;

a ball of hard material in said radial bore, the diameter of said ballbeing greater than the thickness of the wall of the drive shaft definingthe circumference of the insert housing bore so that a portion of saidball extends outwardly of the outer surface of the drive shaft when inthe release position; and

a sleeve slideable longitudinally on the drive shaft,

said sleeve having a bore part with an internal diameter of sufficientsize to snugly receive the drive shaft but to be freely slideablethereon and with another part having a bore, the internal diameter ofwhich is greater than the outside diameter of the drive shaft, therebeing acam surface between the sleeve bores and, with the sleeve in oneposition, the ball is in its usual release position, sliding the sleeveto another position, causing the cam surface to engage the ball andforce it inwardly to pass inwardly on a portion of the insert.

2. The invention defined by claim 1, wherein there is a bore through themeans for retaining the insert in the insert bore, the bore through saidmeans being substantially the same diameter as the tool shaft bore.

3. The invention defined by claim 2, wherein the means for retaining theinsert in its housing bore comprises a nut threadably connected to thedrive shaft, and the bore through said nut is axially aligned with thebore in the insert and the bore in the drive shaft, into which bores thecutting tool is adapted to be inserted.

4. The invention defined by claim 2, wherein there are a plurality ofradial bores annularly and equally spaced apart and a plurality of ballsoperably disposed in the respective radial bores.

5. The invention defined by claim 3, wherein the inner end of the nuthas a part for retaining the insert in position and for adjustablyvarying the length of the cavity in which the resilient insert reposes.I

6. The invention defined by claim 4, including stop means for limitinglongitudinal movements of the sleeve whereby, when the sleeve is at onelimit of movement, the balls are in the larger diameter part of thesleeve and, when said sleeve is at the opposite limit of movement, theballs are held entirely within the radial bores to effect clamping of arotatable tool shaft in the axially-aligned bores.

7. The invention defined by claim 6, wherein there is anoutwardly-flared space from the tool shaft bore to the insert-housingbore.

8. The invention defined by claim 6, wherein the cam in the sleeve isinclined outwardly.

9. The invention defined by claim 6, wherein the sleeve cam is inclinedinwardly.

10. The invention defined by claim 9, including an annular stop on thedrive shaft adjacent the inner end of the sleeve for engagement by thesleeve when moved to its inward clamping position. i

11. The invention defined by claim 3, wherein there are a plurality ofradial bores into the insert-housing bore, said radial bores beingequally spaced apart; a spherical ball in each of said radial bores, apart of said nut at its inner end retaining the insert and adapted toenter the inserthousing bore to control and limit said inserts axialexpansion under compression; and stop means limiting sliding movement ofthe sleeve in either direction, the balls being disposed in the largerdiameter part of said sleeve when said sleeve is inthe release positionat one limit of movement, said balls being forced inwardly within theirrespective radial bores when the sleeve is moved to the opposite,secured-limit position, there being an outwardly-flaring space betweenthe tool shaft bore and the insert-housing bore.

12. A clamping device for operably holding rotatable tools, comprising:i

a drive shaft adapted to have one end connected to a source of power andhaving its other end free, said drive shaft having a free end portionwith a tool shaft bore extending axially from its free end for operablereception of the shaft of a rotatable tool, said bore having anenlarged, insert-housing bore adjacent the free end of said drive shaft,there being a plurality of radial bores intersecting the enlarged,insert-housing bore approximately at its longitudinal center;

means for retaining the insert in said insert-housing bore, said meanshaving an axial bore therethrough of substantially the same diameter asthe tool-shaft rotatable tool shaft disposed in said insert bore.

1. A clamping device for operably holding rotatable tools, comprising: a drive shaft adapted to have one end connected to a source of power and having its other end free, said drive shaft having a free end portion with a tool shaft bore extending axially from its free end for operable reception of the shaft of a rotatable tool, said bore having an enlarged insert housing bore adjacent the free end of said drive shaft, there being at least one radial bore extending from the surface of the shaft into the enlarged insert housing bore; a resilient cylindrical insert in said insert housing bore, said insert having an axial bore therethrough of substantially the same diameter as the tool shaft bore and axially aligned therewith; means for retaining said insert in said insert housing bore; a ball of hard material in said radial bore, the diameter of said ball being greater than the thickness of the wall of the drive shaft defining the circumference of the insert housing bore so that a portion of said ball extends outwardly of the outer surface of the drive shaft when in the release position; and a sleeve slideable longitudinally on the drive shaft, said sleeve having a bore part with an internal diameter of sufficient size to snugly receive the drive shaft but to be freely slideable thereon and with another part having a bore, the internal diameter of which is greater than the outside diameter of the drive shaft, there being a cam surface between the sleeve bores and, with the sleeve in one position, the ball is in its usual release position, sliding the sleeve to another position, causing the cam surface to engage the ball and force it inwardly to pass inwardly on a portion of the insert.
 2. The invention defined by claim 1, wherein there is a bore through the means for retaining the insert in the insert bore, the bore through said means being substantially the same diameter as the tool shaft bore.
 3. The invention defined by claim 2, wherein the means for retaining the insert in its housing bore comprises a nut threadably connected to the drive shaft, and the bore through said nut is axially aligned with the bore in the insert and the bore in the drive shaft, into which bores the cutting tool is adapted to be inserted.
 4. The invention defined by claim 2, wherein there are a plurality of radial bores annularly and equally spaced apart and a plurality of balls operably disposed in the respective radial bores.
 5. The invention defined by claim 3, wherein the inner end of the nut has a part for retaining the insert in position and for adjustably varying the lengTh of the cavity in which the resilient insert reposes.
 6. The invention defined by claim 4, including stop means for limiting longitudinal movements of the sleeve whereby, when the sleeve is at one limit of movement, the balls are in the larger diameter part of the sleeve and, when said sleeve is at the opposite limit of movement, the balls are held entirely within the radial bores to effect clamping of a rotatable tool shaft in the axially-aligned bores.
 7. The invention defined by claim 6, wherein there is an outwardly-flared space from the tool shaft bore to the insert-housing bore.
 8. The invention defined by claim 6, wherein the cam in the sleeve is inclined outwardly.
 9. The invention defined by claim 6, wherein the sleeve cam is inclined inwardly.
 10. The invention defined by claim 9, including an annular stop on the drive shaft adjacent the inner end of the sleeve for engagement by the sleeve when moved to its inward clamping position.
 11. The invention defined by claim 3, wherein there are a plurality of radial bores into the insert-housing bore, said radial bores being equally spaced apart; a spherical ball in each of said radial bores, a part of said nut at its inner end retaining the insert and adapted to enter the inserthousing bore to control and limit said insert''s axial expansion under compression; and stop means limiting sliding movement of the sleeve in either direction, the balls being disposed in the larger diameter part of said sleeve when said sleeve is in the release position at one limit of movement, said balls being forced inwardly within their respective radial bores when the sleeve is moved to the opposite, secured-limit position, there being an outwardly-flaring space between the tool shaft bore and the insert-housing bore.
 12. A clamping device for operably holding rotatable tools, comprising: a drive shaft adapted to have one end connected to a source of power and having its other end free, said drive shaft having a free end portion with a tool shaft bore extending axially from its free end for operable reception of the shaft of a rotatable tool, said bore having an enlarged, insert-housing bore adjacent the free end of said drive shaft, there being a plurality of radial bores intersecting the enlarged, insert-housing bore approximately at its longitudinal center; means for retaining the insert in said insert-housing bore, said means having an axial bore therethrough of substantially the same diameter as the tool-shaft bore; a resilient, cylindrical insert of rubber in said insert-housing bore, said insert having an axial bore therethrough aligned with the tool-shaft bore and the bore through the means for retaining the insert in its bore; balls in the respective radial bores, said balls extending outwardly of the drive shaft when in a release position; and means for forcing said balls inwardly for exerting pressure on said insert to compress same against a rotatable tool shaft disposed in said insert bore. 